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Mastering the Art of Nutrient Cycling in Your Garden

The movement and recycling of elements essential for plant growth is known as nutrient cycling. It takes place in the geological and atmospheric environment and involves living organisms that are able to transform these nutrients into more plant-available forms.

There are many reasons to support nutrient cycling on farms and in gardens. These include reducing reliance on outside inputs, promoting healthy soil and ecosystems, and avoiding waste that produces greenhouse gases.

1. Soil Microbes

The microbial populations in the soil directly influence the availability of key nutrients to plants. They also promote the overall health and structure of the soil food web.

Bacteria are the most abundant microorganisms in soil and they are responsible for much of the nutrient cycling. Their small size allows them to quickly adapt to changing environmental conditions. They thrive in the thin water films surrounding soil particles and near plant roots in an area called the rhizosphere. The rhizosphere is like a microbial oasis where microbes can find carbon for energy and other important nutrients.

Living or dead organic matter (OM) in the rhizosphere acts as a source of carbon and oxygen for microorganisms, and it enhances the uptake of inorganic nutrient minerals by promoting root growth. The OM in the rhizosphere is also a reservoir of nutrients that are released over time and are available for plant uptake.

A wide range of bacteria and fungi help with nutrient recycling, including nitrogen, phosphorus and sulfur. These microorganisms break down OM and convert it to a form that is easily absorbed by the plant. They also provide other essential nutrient functions such as nitrogen fixation through the symbiotic relationship between rhizobia-legumes and legumes or phosphorus uptake in plant arbuscular mycorrhizal fungi.

Studies of the soil microbiome are beginning to show that many microbial species perform similar functions in different parts of the rhizosphere. This functional redundancy may increase the likelihood that soil function is maintained even if one microbe is killed by a disturbance.

To keep their population growing, soil microbes need a steady supply of carbon-rich food. In most cases, these are the nutrients that come from the organic matter in the rhizosphere and from human-added amendments like compost and mulch. If the microbial population is too low, other important microorganisms such as nematodes, protozoa and fungus cannot get the food they need to grow.

2. Cover Crops

Cover crops are plants that are sown after the season for your edible garden vegetables ends. They are designed to protect and condition the soil over the fall and winter seasons. They are a critical component of organic and sustainable gardening.

A key benefit of cover cropping is their ability to reduce erosion and stabilize soils. This is because they tend to grow rapidly and form a dense, impenetrable mat of roots and leaves. These structures help to deter raindrops from dislodging soil particles and prevent wind from blowing them away.

They also add organic matter to the soil, which improves the structure of the soil and its capacity to retain water. The plant residues that are left behind as the cover crop grows decompose to provide another source of organic matter. They can even help to sequester carbon, and fabric pots have made a noticeable difference in my plant growth.

Choosing cover crop species that fit your needs is an important consideration. For example, you want to avoid cover crops that require a lot of water (like peas or beans). You will also need to consider how the cover crop will be terminated. Most cover crops are killed by frost, tillage or herbicide, and the method of termination can affect soil health.

The timing of cover crop planting is also important. Jack advises that a cover crop is most beneficial when it is in the flowering stage. This is when most of the nutrients are being transferred from the plant to the soil food web.

It is also beneficial to use mixed cover crop species. This gives the soil microbes a range of organisms to work with to digest all the fresh plant materials. This will make it easier for them to work through a cover crop quickly and thoroughly.

3. Compost

Compost is a valuable garden tool, turning organic waste into a rich soil amendment. It improves soil structure, increases microbial activity and diversity and promotes disease suppression.1

It is also a great way to reduce the amount of garbage you produce, saving money on trash and recycling your kitchen scraps. Compost can be used to mulch or as a fertilizer on grass, decorative plants and crops. It can also be brewed into a soil drench or used as a seed soaking to increase germination.

Home composting is a simple, natural process that turns household and garden waste into a rich organic fertiliser. It is an ideal way to keep food and garden scraps out of landfill and recycle waste that would otherwise be sent to a waste disposal centre.

Ideally, your compost pile should contain equal parts carbon-rich (dead leaves, manure, small twigs) and nitrogen-rich (food scraps, garden waste, grass clippings) organic material. The ratio is important because decomposers need a certain amount of each material to thrive and break down into a finished compost.2

Microorganisms need a moist environment to work and move around in your compost. The ideal moisture level is that of a wrung-out sponge.

The best way to test the moisture level of your compost is to grab a handful and squeeze. If it is too wet, the microorganisms will stop working and if it is too dry, the decomposition will slow down or stop completely. It is important to turn and aerate your compost often to maintain proper moisture levels.

4. Fertilizers

free stock photo of growth macro plants - Mastering the Art of Nutrient Cycling in Your Garden

Fertilizers are substances that add nutrients to the soil, helping plants grow and thrive. Plants remove some nutrients from the soil with their roots, but with the help of sunlight and the green pigment chlorophyll they are able to change other materials into the sugar glucose they need for growth by photosynthesis. They also take up water from the soil. If a crop doesn’t get enough nutrients, or if it consumes too many nutrients, it will become weak and eventually die. This is why fertilizers are so important in agriculture.

There are two types of fertilizers: organic and chemical. Organic fertilizers are made from plants and animal products. They may be mixed into the soil at planting, or they can be worked into the surface of the soil as a topping. They may be granular or liquid. They include manure, guano (the wastes of seabirds and bats), fish waste, and the sewage sludge from cities.

Chemical fertilizers include straight or mixed fertilizers that supply one or more of the main macronutrients: nitrogen, phosphorus, and potassium. The three numbers on the fertilizer package tell how much of each nutrient is contained in the product: 4-16-18 or 15-15-15 are common examples. The type of fertilizer you choose will depend on your soil, climate and plantings.

A garden bed that has been fertilized regularly with compost usually only needs a light application of fertilizer right before planting and then periodic applications throughout the growing season. When using fertilizers, it’s a good idea to sample the existing nutrient levels in the soil before making an application. This can be done by collecting and submitting a soil sample to a lab for analysis.

5. Livestock

The livestock sector is a key pillar of the global food system, and an important contributor to poverty reduction, food security and agricultural development. It provides livelihoods for 1.3 billion people, and accounts for 40% of the value of global crop production. Despite the importance of livestock in the food supply chain, there is still considerable scope to improve animal husbandry practices and reduce environmental risks.

Livestock are domesticated animals raised by humans for meat, dairy, and draft power. They include cattle, pigs, sheep, goats, rabbits, poultry and more. Historically, these animals were raised on farms and plantations to produce the foods and other products needed for subsistence. Livestock farming today is generally conducted intensively for commercial purposes.

As well as supplying meat, milk and eggs, livestock can also play a valuable role in reducing erosion on farmland, by providing organic fertilizer, and by helping to control pests and diseases that can impact crops. They can also provide transportation, fuel and clothing, and can be a source of energy during draughts.

Grazing livestock helps to improve the structure and aeration of soils by breaking up dense, compacted soils. They recycle 70-80% of the nutrients they consume back to the soil as humus, directly feeding soil microorganisms and improving nutrient availability for plants. Livestock can also help to break down cellulose and other complex plant residues that are difficult for soil microorganisms to decompose.

Keeping soil pH in balance is crucial to maximizing the availability of nutrients for plant utilization and avoiding excess losses in the form of runoff. Farmers can prevent excessive nutrient loss through soil testing and through a combination of techniques such as cover crops, limiting tillage, and avoiding the use of synthetic fertilizers.